Blowing agent additive

ABSTRACT

Aromatic sulphinic acids and their salts are used as activators for lowering the decomposition temperature of azodicarbonamide, which have a higher activity than the conventional auxiliary blowing agents. Moreover, no premature liberation of gas takes place.

v United States Patent [1 1 3,803,060 Roos et al. Apr. 9, 1974 BLOWINGAGENT ADDITIVE 260/899, 260/54 [75] Inventors: Ernst Roos; TheoKempermann, [5 1] int. Cl. C08f 47/10, C08c 17/10, C08g 22/44 o of C oga e b e of Search R, 2.5 HA, porbwahn; Gunter Dammann, 260/2.5 HB, 2.5H, 2.5 AB, 724 Cologne, all of Germany [56] References Cited [73]Ass1gnee: Bayer AG, Leverkusen, Germany OTHER PUBLICATIONS Filed? 17,1972 Blowing Agents; Henry R. Lasman; Encyclopedia of [21] Appl No;218,239 Polymer Science and Technology page 548.

Primary Examiner--Wilbert J. Briggs, Sr. [30] Foreign ApplicationPriority Data Attorney, Agent, or Firm-Connolly and Hutz Jan. 18, 1971Germany 21021772 ABSTRACT [52] U.S. Cl 260/2.5 AE, 260/2.5 R, 260/2.5 H,

260/2.5 E, 260/2.5 HA, 260/2.5 HB, 260/18 TN, 260/23 XA, 260/2.5 P,260/23.7 M, 260/31.8 M, 260/31.8 HR, 260/3l.8 PQ, 260/3l. 8 R, 260/28.5AV, 260/41 R, 260/41.5 R, 260/45.75 K, 260/45.75 R, 260/724, 260/829,260/859 PV, 260/894,

Aromatic sulphinic acids and their salts are used as activators forlowering the decomposition temperature of azodicarbonamide, which have ahigher activity than the conventional auxiliary blowing agents.Moreover, no premature liberation of gas takes place.

20 Claims, 1 Drawing Figure BLOWING AGENT ADDITIVE perature in the rangeof 200C to 210C. When it is present in mixtures, gas starts to beevolved at about l60C (loc.cit., page 70, righthand column). In manycases, however, it is desired for decomposition of a20- dicarbonamide totake place at lower temperatures than this. Decomposition at a lowertemperature would reduce the thermal stresses to which mixtures foamedwith azodicarbonamide are subjected and would also enablehigherdecomposition rates and shorter operating cycles to be achieved.

It is already known that the decomposition temperature ofazodicarbonamide is reduced by the addition of one or more so-calledauxiliary blowing agents which have a lower decomposition temperaturethan azodicarbonamide (see German Offenlegungsschrift No. 1,5 69,535)

The use of these auxiliary blowing agents, however, frequently resultsin premature decomposition of the blowing agent'in the course ofproduction and processing of the mixtures containing them because theauxiliary blowing agents used as activators'for azodicarbonamide, forexample benzene sulphohydrazide, decompose at relatively lowtemperatures, e.g. at 80C (see loc.cit. page 71, lefthand column, lastparagraph). Consequently, unwanted decomposition of the auxiliaryblowing agent may occur during storage of mixtures which contain suchcombinations of blowing agents. This is manifested e.g. in the case ofrubber mixtures by premature expansion and in the case of plastics, e.g.PVC pastes, by gassing.

We now have found that aromatic sulphinic acids and their saltsrepresented by the following general formula l l R The sulphinic acidsand sulphinates used according to the invention surprisingly function asactivators in lowering the decomposition temperature of azodicarbonamideused as blowing agent and in this respect they have a higher activitythan the conventional auxiliary blowing agents such as benzenesulphohydrazide. Moreover, they do not give rise to premature liberationof gas since they are not themselves blowing agents.

The following are mentioned as examples of radicals R to R Straightchain or branched'chain alkyl groups having from 1 to 4 carbon atoms,such as methyl, ethyl, n-propyl, isopropyl, 'n-butyl, sec.-butyl,tert.-butyl or isobutyl; the halogen atoms may bechlorine, fluorine orbromine.

Suitable metal cations M are especially elements of the first Main Groupand the'second Main Group and sub-Group and fourth sub-Group of thePeriodic System as well as heavy metals. The following are mentioned asspecific examples of suitable metal cations: Lithium, sodium, potassium;magnesium, calcium, barium, zinc, cadmium, mercury, tin, lead and iron.

Groups with ammonium nitrogen represented by M may, for example, begroups of the following general formula wherein R R and R represent,independently of each other, hydrogen or an aliphatic radical, theradicals R and R may together with the ammonium nitrogen form part of a5, 6 or 7-membered ring system which in the case of a 6-membered ringmayin addition contain hetero atom such as oxygen, a nitrogen atomoptionally substituted by a C, to C alkyl radical or a sulphur atom.

The aliphatic radicals R to R may be straight chain or branched chainalkyl radicals having 1 to 4 carbon atoms optionally substitutedby'phenyl or they may be cycloalkyl radicals with from 5 to 7 carbonatoms. The following are mentioned as examples of alkyl and cycloalkylradicals: Methyl, ethyl, n-propyl, isopropyl, nbutyl, sec-butyl,isobutyl, tert.-butyl, benzyl, phenylethyl, phenyl-n-propyl,cyclopentyl, cyclohexyl and methylcyclohexyl.

The following are mentioned as specific examples of compounds which maybe used according to the invention:

Benzene sulphinic acid;

lithium benzene sulphinate;

sodium benzene sulphinate;

potassium benzene sulphinate;

magnesium-di(benzene sulphinate);

calcium di-(benzene sulphinate);

zinc-di-(benzene sulphinate);

barium di-(benzene sulphinate);

cadmium di-(benzene sulphinate);

lead di-(benzene sulphinate);

ammonium benzene sulphinate;

trimethylammonium benzene sulphinate;

tertiary butyl ammonium benzene sulphinate;

cyclohexyl ammonium benzene sulphinate;

benzyl ammonium benzene sulphinate;

p-toluene sulphinic acid;

lithium p-toluene sulphinate; sodium p-tolu ene sulphinate; potassiump-tolu ene sulphinate; magnesium bis-(p-toluene sulphinate); calciumbis-(p-toluene sulphinate); barium bis-(p-tolu ene sulphinate); zincbis-(p-toluene sulphinate); a mium -(pol n' h t lead bis- ('p-toluenesulphinate); ammonium p-tolu ene sulphinate; diethylammoniurn p-toluenesulphinate;

'di-secbutylammonium p-toluene sulphinate;

cyclohexyl-rriethylammonium-p-toluene sulphinate; morpholinium-p-toluenesulphinate; thiornorpholinium-p-toluene sulphinate;

' p pc s nium-p-tv u nc p ts;

p-lc hlorobenzene sulphinic acid; lithiump-chlorobenzene sulphinate;

sodium p-chlorobenzene sulphinate;

potassium p-chlorobenzene sulphinate; magnesium bis- (p-chloroben zenesulphinate); calcium bis-(p-chlorobenzene sulphin'ate bariumbis-(p-chlorobenzfene sirlp'hinate);

zinc bis-(p-chlorobgr zene sulphinate);

' cadmium I bis-(p-chlorobenzene su'lphinate);

lead bis'-( p-chlorob'enzene sulphinate);

ammonium p-chlorobenzenesulphinate; triethylammonium p-chlorobenzenesulphinate; dicyclohexylammonium pchlorobenzene sul'phinate;

pyrrolidinium-p-chlorobenzene sulphinate; piperidinium-p-chlorpbenzerie'sulphinate;

. 2,4-dimethylbenzene sulphinic acid;

lithium 2,4-dimethylbenzene sulphinate;

sodium 2,4:dimethylbenzene sulphinate; potassium 2,4 -dimethylbenzenesulphinate; magnesium-bis-(2,4-dimethylbenzene sulphinate);icalcium-bis-(Z,4-dimethylbenzene sulphinate); bariumbis-(2-,4-dimethylbenzene sulphinate);

, zinc-bis-(2,4-dimethylbenzene sulphinate);

cadmium-bis-( 2,4-dimethylbenzene sulphinatelead-bis-(2,4-dimethylbenzene sulphinate); ammonium 2,4-dimethylbe nzenesulphinate; 2,5}dimethylbenzene sulphinic acid;

sodium 2,5-dimethylbenzene sulphinate;

zinc bis-(2,5;dimethylbenzene sulphinate); 3,4f-jdimethylbenzenesulphinic acid; I sodium 3,4-dimethylbenzene sulphinate;

zinc bis-( 3,4-dimethylbenizene sulphinate); 2 chloro 4 -methyl-benzenesulphinic acidg' sodium'2-chloro-4-methylfbenzene sulphinate; zinc bis-(2-chloro-4-methyl-benzene sulphinate); 2methyIMmhlorO-benZene"sulphinie acid,- sodium2-methyl-4-chloro-benz'e'ne' sulphinate;

'zinc bis.-( 2 methyl-4-chloro-benzene sulphinate); "p-fluorobenzenesulphinic acid;

sodium p-fluorobenzene sulphinat e; zinc bis-( p-fluorobenzene.sulphinate p-bromobenzene sulphinic acid; I sodium p-bromoben'zenesulphinate;

' zinebis-( p-bromo'benzene sulphinate p-tertiary" butyl-benzenesulphinic acid;

I sodium p-te'rtiary-butyl-benzene sulphinate;

ziricbis-K 2 ,3 ,4,5 ,ti pentamethyl-ben'zene sulphinate zinc bis-(2,3,4,5,o-pentachloro-benzene sulphinate).

Suitable rubbers and plastics for the production of cellular or porousarticles using azodicarbonamide and activators based on sulphinic acidsor sulphinates are e.g. natural rubber or synthetic, rubber-likepolymers obtained e.g. from conjugated diolefmes such as butadiene,chlorobutadiene, dimethylbutadiene, isoprene and its hontologues; orcopolymers of such conjugated mannegfor example on mixing rollers attemperatures from l20l50C by mixing for 5-30 minutes, in internal mixersat room temperature by mixing for 5-30 minutes or in mixingvesselsequippedwith stirrers at room temperature by mixing for5-l20minutes. The activators may be added at the same time as the otherconstituents of the mixture but are preferably added at the start, thatis from when azodicarbonamide is first used as blowing agent. Thequantity of activators used according to the invention should be intherange of from about 0.5- to 30 percent by weight, preferably 2 to 10percent by weight, based on the blowing agent, in

the case of mixtures based on n'atural or synthetic rubher. In caseswhere synthetic resinsare used, e.g. polyethylene, polypropylene,polyvinyl chloride or polystyrene, the quantity. of activators usedaccording to the invention should by in the range-of fromabout 0.1 to 5parts by weight, preferably 0.5 to 3.0 parts by weight, based on I partby weight of the blowing agent.

After addition to natural and/or synthetic rubber the mixturesthus-obtained are heated'at the usual vulcanization temperatures from-130? to 300C.

After addition'toplastics the expansionaccording to the invention takesplaceafterf heating at temperatures from 160 to 220C. If necessarythecrude material can,

be expanded again at temperatures' from 90 to 120C;

When usingiakpressureless process films andpastes pass; through Jafgelatinizing channelj heated "to l 20-250C.for a period of 0.5-4.0minutes.

. Themixtureswhich are to betreatedrnayalso conj- 'tlainconventionalauxiliary agents, e.g. active. or inac-.

tive fillers such as carbon black orchalk, antioxidants, antiozonants,stabilizerssuchas salts of lead, cadmium, calcium, zinc, tin or barium,waxes, dyes, pigments, zinc'oxide, fattyacidsriuch as ste'aric acid,mineral oils, plasticizers such as dioctyl phthalate, butyl nonylphthalate, butyl benzyl -phtha late,'dibutyl phthalate, di-

butyl adipate or tricresyl phosphate, lubricants, peroxides, vulcanizingagents such as sulphur and-accelerators. The following are examples ofsuitable accelera tors: Thiazoles, guanidines, dithiocarbarnates,thiurams and Z-mercaptoimidazoline;

The method of preparingthe aromatic sulphinic acids and their salts (l)is 'alreadyknown.

S02 Na Nil-2S0; NaC1+ H20.

The alkali metal salts may also advantageously be 25 used for thepreparation of free aromatic sulphinic acid, e.g'. according to thefollowing equation:

Ammonium sulphinates are obtained by reacting the free sulphinic acidswith ammonia in accordance with 35 the following equation:

Substituted ammonium sulphinates are obtained by reacting the freesulphinic acids with amines such as the deprotonised compounds offormula (11). The following reaction equation illustrates byway ofexample the reaction of p-toluenesulphinic acid with morpholine:

The following Examples serve to illustrate the invention. The figuresentered in the Tables represent parts by weight unless otherwiseindicated.

EXAMPLE 1 The graphs in FIG. 1 represent the rate of liberation of gasfrom the azodicarbonamide alone and with the aid of various activators.The rate of liberation of gas was determined on the principle ofmolecular weight determination by the method of Victor Meyer.

Curve A represents the rate of decomposition of 1 g of pureazodicarbonamide suspended in 1 g of tricresyl phosphate at 192C.

Curve B represents the rate of decomposition of l g of a mixture of 0.9g of azodicarbonamide and 0.1 g of benzene sulphonhydrazide suspended inl g of tricresyl phosphate at 192C.

Curve C represents the rate of decomposition of 1 g of a mixture of 0.9g of azodicarbonamide and 0.1 g of zinc dibenzene sulphinate suspendedin l g of tricresyl phosphate at 192C.

The curve clearly shows that zinc di-benzene sulphinate accelerates thedecomposition of azodicarbonamide for a greater extend than benzenesulphohydrazide.

EXAMPLE 2 The following mixtures were prepared (See Table l )1 TABLE 1Mixture No. l 2 3 4 5 6 7 8 9 10 11 Ethy1ene-' 100.0 100.0 100.0 100.0100.0 100 0 100.0 100.0 100.0 100.0 100.0 propylene-(Ilene terpolymerZinc oxide 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Steurie acid 1.01.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 fine carbon 40.0 40.0 40.0 40.040.0 40.0 40.0 40.0 40.0 40.0 40.0 black powdered chalk 75.0 75.0 75.075.0 75.0 75.0 75.0 75.0 75.0 75.0 75.0 naphthenic 75.0 75.0 75.0 75.075.0 75.0 75.0 75.0 75.0 75.0 75.0 mineral oil Z-mercaptobcn- 0.5 0 50.5 0 5 0.5 0.5 0.5 0.5 0.5 r 0.5 0.3 zothiazole tetramethylthi- 1.5 1.51.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 uramic monosulphideN,N-diphenylthiourea [,0 0 1.0 1.0 1,0 1.0 1 0 1 0 1.0 1 O 1 0 sulphur1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 azodicarbonamide 30". 3.03.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0

benzene 0.45 sulphohydrazide (for comparison) zinc di-(henzcne 0.15

TA BLE l.- Continued Mixture No. l 4

sulphinate) sodium benzene sulphinate zinc bispchlorobenzenc sulphinatc)lead di-(benzcne sulphinate) cadmium di-(toluene sulphinate) cadmiumdi(benzene sulphinate) sodium toluene sulphinate Magnesium di-(benzenesulphinate) sodium p-chlorobenzcne sulphinate The mixtures were preparedon mixing rollers and ex-- truded to form profiles of constantcross-section. These profiles were then placed in a suitable vulcanizingmould. The unvulcanized profiles were cut into equal lengths beforebeing introduced into the moulds and 30 only partly filled the moulds sothat complete filling of the moulds during and after vulcanization waspossible only after complete liberation of gas from azodicarbonamide.vulcanization was carried out in a press at 160C for 20 minutes.

The densities (g/cm) of the vulcanized and expanded profiles are shownbelow:

Mixture No.

Density (g/cm) 0.83 0.56 0.54

The figures in this table show that insufficient gas is evolved fromazodicarbonamide at 160C without anf activator present and consequentlyazodicarbonamidei does not sufficiently expand the mixture. In thatcase,i

is that the sulphinates used show the same activator ef- .fect in aquantity of 5 percent (based on azodicarbon- 'amide) as benzenesulphohydrazide in a quantity of 15 percent. 7 I

EXAMPLE 3 nization and foamed at the same time. The time of stay' in thecuring oven was Zminutes.

The results obtained with formulations 12 to 23 are summarized in theTable below.

MiXlUlC NO. l2 l3 l4 l5 l6 l7 l8 19 '20 2| 22 23 Density Y (g/cm) 0.440.22 0.25 0.74 0.60 0.62 1.04 0.67 0.65 1.03 0.37 0.55

a profile with relatively high density is obtained mixture No. 1.) Allthe other mixtures (Nos. 2 to 1 1)which 65 contained activators inaddition to azodicarbonamide; completely filled the moulds. This ismanifested by thelow densities. The surprising finding in thisexperiment It is clear that the mixtures containing azodicarbonamide asblowing agent and zinc di-(benzene sulphi- 'nate) or zincdi-(4-chloro-benzenesulphinate) asactivator result in products with alower specific weight than the corresponding comparative formulations.

TABLE 2 Mixture No. 12 13 14 15 16 17 18 19 20 21 22 23 PVC paste forcomparison (K 55 55 55 value approx. 70) Suspension PVC (K-value 50 5050 approx. 70) Ethylene-vinyl acetate-vinyl 100 100 100 100 100 100chloride terpolymer Alkylsulphonic acid ester of 45 45 45 phenolPolyurethane 50 50 50 Diisononylphthalate 2O 20 20 Azodicarbonamide 2.02.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Ba/Cd stabilizer (11.) 1.5Dibutyl tin mercaptide 1.0 1.0' 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Zincdi-(benzenesulphinate) 1.5 1.5 1.5 1,5 Zinc di-(4'ch1orobenzene 1.5 1.51.5 1.5 sulphinate) Chalk 5.0 5.0 5.0 5.0 5.0 5.0 Ester Wax, partlysaponified 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 12 hydroxystearic acid0.2 0.2 0.2

EXAMPLE 4 The resulting densities of the end products obtained TABLE 3from formulations 24 to 37 are entered at the end of Table 3. 1

The results show that mixtures which contain zinc di-(benzenesulphinate) or zinc di-(4-ch10robenzene sulphinate) as activatorgive rise to products with a lower specific gravity than thecorresponding formulations used for comparison both in the case wherethe blowing agent used in azodicarbonamide and in the case where amixture of azodicarbonamide and benzene sulphohydrazide in the ratio of85:15.

Mixture No. 24 25 26 27 28 29 Vinyl chloride-vinyl acetate copolymersuitable for preparing a paste PVC paste (K-valuc approx.Di-Z-cthylhcxyl phthalatc dibutyl tin mercaptide zincdi-(benzenesulphinate zinc di-(4- chlorobenzenc sulphinate) dibasic leadphthalate sodium bicarbonate azodicarbonamide azodicarbonamideI- benzenesulphohydrazide :15

Den sity-(g/cm) at Den sitytg/cm) at EXAMPLE Mixtures Nos. 38 to 51represented in Table 4 were prepared.

(approximately 850 g/m those which also contain zinc (ii-(benzenesulphinate) or zinc di-(4- chlorobenzene sulphinate) result in productswith a lower specific gravity than the products which are ob- All thecomponents of the formulations were 5 tained from the correspondingcomparative mixtures. homogenised on a three roll mill. This effect isall the more obvious the shorter the time The pastes thus obtained wereapplied with a coating of stay in the gelatinizing channel. knife to asiliconised support fabric and then gelati- In addition, it is observedthat such mixtures give rise nized in a gelatinizing channel heated withcirculating to products with a substantially higher proportion of airand foamed up. v open pores than those which contain e.g. a dibasic leadThe residence times, of the mixtures which were to be phthalate asactivator. foamed and the temperature in the gelatinizing channel Thesame applies to mixtures which contain as blowwere varied. ing agent amixture of azodicarbonamide and benzene The results obtained forformulations 38 to 51 are sulphohydrazide in the proportion of 85:15instead of summarised in Tables 5 and 6. azodicarbonamide alone. 7

It is clear from the results that when mixtures con- Similar results areobtained when the gelatinizing taining az'odicarbonamide are applied inequal amounts temperature is varied instead of the time of stay.

TABLE 4 Mixture No. 38 39 40 41 42 43 44 45 46 v 47 4s 49 50 51 PVCpaste 50 50 50 50 50 50 50' 50 (k-valuc approximately Vinyl 50 50 50 5050 50 chloride vinylacctatc copolymer which can be made up to a pasteAlkyl 50 50 50 50 50 50 sulphonic acid ester of phenol Di-(Z-ethyl- 37.537.5 37.5 37.5 37.5 37.5 37.5 37.5 h'exyl phthalate I Benzyl butyl 12.512.5 12.5 12.5 12.5 12.5 12.5 12.5 phthalate Azodicarbonamide 1.0 1.01.0 1.0 1.0 1.0

1 Azodicarbon- 1.0 1.0 1.0 l .0 1.0 1.0 1.0

amide/benzenesulphohydrazide :15 Dibutyl tin 1.0 1.0 1.0 1.0 1.0 1.0 nercaptide Dibasic lead 1.5 1.5

phthalate V W Zinc 1.5 1.5 1.5 1.5 di-(bcnzenc sulphinate) zinc 1.5 1.51.5 1.5 Iii-(4- chlorobenzene; sulphinate TABLE 5 Minute No. Density(g/cm") at time of stay in minutes in gelatinizing channel. temperatureC 3.43 2.66 1.71 1.35 1

.- TABiEfi Mixture No. Density (gfcm at time of Sta} 3.43 minutes ingelatinizing channel in dependence upon the temperature chine and thesamples obtained were tested to deter- EXAMPLE 6 The following mixtureswere prepared (see Table 7).

mine their density and hardness. The following results were obtained:

TABLE 7 Mixture NO 52 53 54 55 Styrene-butadiene copolymer (styrenecontent approx/23.5%) 70.0 70.0 70.0 70.0

Styrene-butadiene copolymer (styrene content approx. 30.0 30.0 30.0 30.0

Coumarone resin 5.0 5.0 5.0 5.0

Precipitated silicic acid containing a small proportion 45.0 45.0 45.045.0 of calcium silicate Aromatic mineral oil 2.5 2.5 2.5 2.5 I

Zinc oxide in 5.0 5.0 5.0

Stearic acid 3.0 3.0 3.0 3.0

Ethylene glycol 1.1 1.1 1.1 1.1

Diphenylamine derivative 1.0 1.0 1.0 1.0

Sulphur 2.5 2.5 2.5 2.5

Z-Mercaptobenzothiazole 1.5 1.5 1.5 1.5

Azodicarbonumidc 3L5 3.5 3.5

Azodicarbonamide/benzcncsulpho- 3.5 hydrazidc 15 Zinc (ii-(benzenesulphinate) 0.175

Zinc bis-(p-chlorobenzcne sulphinute) 0.175

The m xtures were prepared on mixing rollers and ro- 55 Mixture 52 53 5455 lled out into plates about 10 mm in thickness. 420 g of each mixturewere then introduced into a mould mea- Density (g/cm) 0.41

' 200 x 200 x s m d' t surmg mm mm m correspon ing 0 outer skin 67 54 52filling the mould by 103 volumes percent) and then Split surface 60 4e42 44 pre-cured for 12 minutes at 150C at a pressure of 80 kg wt/cm in asteam heated press. The plates were removed from the mould at the end ofthis time and were found to have undergone substantial expansion. Theseexpanded plates were then placed in a hot air chamber (C) for 30 minutesto complete curing.

After cooling, the plates were split in a splitting ma- EXAMPLE 7 Thefollowing mixture was prepared (Table 8).

TABLE 8 Mixture No. 56 Polychloroprene rubber 100,0 Magnesium oxide 4,0Diphenylamine derivative 1,5 Medium thermal black 20,0 Alkylsulphonicacid ester of phenol 30,0 Powdered chalk 45,0 Stearic acid 1,0 Zincoxide 5,0 N,N'-diphenylthiourea Z-Mercaptoimidazolinc 1,0Azodicarbonarnidc 2,7 Zinc-di-(benzenc sulphinate) 0,3

The mixture was prepared on mixing rollers and extruded 'to form aprofil. This profil was then placed in I a suitable vulcanizing mouldand only partly filled it.

vulcanization was carried out in a steam-heated press at 160C for 20minutes. t I Y The vulcanized and expanded profile has a density of Themixtures were prepared on mixing rollers. The mixing temperature wasabout'80 90C. The peroxide was added finally at about 70-80C. Themixtures were then rolled out into plates about 7 mm in thickness and330 g of each introduced into a mould measuring 200 mm X 20 mm X 6 mm(corresponding to filling the mould by 100 volumes percent).

In this way two plates per mixture were placed and then heated for 8minutes, respectively 12 minutes at 160C at a pressure of 80 kg wt/cm onthe surface of v the mouldings. I

At the end of the cited time the plates were removed from the mould andwere found to have undergone substantial expansion. After cooling, theplates were split in a splitting machine and the samples obtained weretested to determine their density and hardness. The following resultswere obtained:

Hardness (Shore A) 4 about 80 The results show that the plates producedfrom azo dicarbonamide without activator have undergone only slight,respectively no expansion whereas the activator zinc-di-(benzene'sulphinate) used effect distinctly more rapid liberation of gas which isexpressed by the lower densities of the product.

EXAMPLE 9 To produce extruded articles made of polyethylene thecommercially available granulates are mixed in suitable mixing devicessuch as internal mixers with 0.3-0.4 percent butyl stearate as anadhesive agent.

Mixing time 5-30 minutes, preferably 10 minutes.-

Thereafter the activator and the azodicarbonamide are added. Anypossible stickiness of the granulate can 'be prevented by4-5 hourstorage at 50 to C.

The processing conditions have been correctly choosen if the extruded orinjection-moulded materials leave the extrusion orifize or the nozzle asa bubblefree melt and if the foaming process starts 1-5 cm away from theorifize or if the foaming takes place upon injection moulding l-5 cmspace.

Temperature program for the extruder:

Feed zone: l30-150C Compression zone: l50-l 70C Metering zone: l-l90CInjection mould: l30l 55l80C starting from the feeding hopper Nozzle:maximum 220C Density of the parts obtained: 0.4-0.5 g/cm What we claimis:

1. A process for the production of a cellular or porous article of atleast one member of the group consisting of natural rubber, syntheticrubber and synthetic resins wherein the process is carried out in thepresence of azodicarbonamide as blowing agent and as an activa-- tor forthe blowing agent, an activating amount of a compound of the formula:

Periodic System or a heavy metal.

3. The process of claim 1 in which M is a group con taining ammoniumnitrogen of the formula:

1 GB H1TIR7 a wherein R and R are, independently of each other, hydrogenor an aliphatic radical or R and R together with after injecting intothe free the ammonium nitrogen form a 5, 6 or 7- membered ring systemwhich in the case of the 6- membered ring may contain an additionalhetero atom optionally substituted by an alkyl radical having 1 to 4carbon atoms or a sulphur atom and R is hydrogen or an aliphaticradical.

4. The process of claim 1 wherein the compound of said formula isp-chlorobenzene sulphinic acid.

5. The process of claim 1 wherein the compound of said formula is sodiumbenzene sulphinate.

6. The process of claim 1 wherein the compound of said formula is zincdi-(benzene sulphinate).

7. The process of claim 1 wherein the compound of said formula is sodiump-chlorobenzene sulphinate.

8. The process of claim 1 wherein the compound of said formula is zincdi-(p-chlorobenzene sulphinate).

9. The process of claim 1 wherein the compound of said formula is zincdi-(p-toluenesulphinate).

10. The process of claim 1 wherein the selected member of said group isa synthetic rubber homopolymer of butadiene, chlorobutadiene,dimethylbutadiene or isoprene or its homologs or a copolymer of saidconjugated diolefins with styrene, a-methylstyrene, acrylonitrile,methacrylonitrile, acrylates or methacrylates.

11. The process of claim 1 wherein the selected member of said group isa synthetic resin selected from the group consisting of polyethylene,polypropylene,.

polyvinyl chloride, polyvinyl acetate, polyvinyl chloride-acetate,polystyrene, polyacrylonitrile, acrylonitrile-butadiene-styrenecopolymer, ethylene-vinyl acetate copolymer, ethylene-propyleneterpolymer, ethylenepropylene copolymer, vinyl chloride-ethylenecopolymer, vinyl chloride-propylene copolymer and polyurethane.

12. The process of claim 1 wherein the compound of said formula is usedin a mixture based on natural or synthetic rubber in an amount of from0.5 to 30 percent by weight based on said azodicarbonamide.

13. The process of claim 1 wherein the compound of said formula is usedin a mixture based on a synthetic resin in an amount of from 0.1 toparts by weight based on 1 part by weight of said azodicarbonamide.

14. A mixture comprising at least one member of the group consisting ofnatural rubber, synthetic rubber and synthetic resins, a blowing agentamount of azodicarbonamide and as an activator for the blowing agent, anactivating amount of a compound of the formula of claim 1.

15. A mixture comprising at least one member of the group consisting ofnatural rubber, synthetic rubber and synthetic resins, a blowing agentamount of azodicarbonamide and as an activator for the blowing agent, anactivating amount of a compoundof the formula of claim 1 in which themetal cation M is an element of the first Main Group, the second Main orsub-Group or the fourth sub-Group'of the Periodic System or a heavymetal or M is a group of the formula atoms or a sulphur atom and R ishydrogen or an aliphatic radical.

16. A mixture comprising at least one member of the group consisting ofnatural rubber, synthetic rubber and synthetic resins, a blowing agentamount of azodi ca'rbonamide and as an activator for the blowing agent,

an activating amount of sodium benzene sulphinate.

17. A mixture comprising at least one member of the group consisting ofnatural rubber, synthetic rubber and synthetic resins, a blowing agentamount of azodicarbonamide and as an activator for the blowing agent, anactivating amount of zinc di-(benzene sulphinate).

18. A mixture comprising at least one member of the group consisting ofnatural rubber, synthetic rubber and synthetic resins, a blowing agentamount of azodicarbonamide and as an activator for the blowing agent, anactivating amount of sodium p-chlorobenzenesulphinate.

19. A mixture comprising at least one member of the group consisting ofnatural rubber, synthetic rubber and synthetic resins, a blowing agentamount of azodicarbonamide and as an activator for the blowing agent, anactivating amount of zinc di-(p-chlorobenzene sulphinate). i

20. A mixture comprising at least one member of the group consisting ofnatural rubber, synthetic rubber and synthetic resins, a blowing agentamount of azodicarbonamide and as an activator for the blowing agent,

an activating amount of zinc di-(p-toluene sulphinate).

2. The process of claim 1 in which the metal cation M is an element Ofthe first Main Group, the second Main or sub-Group or the fourthsub-Group of the Periodic System or a heavy metal.
 3. The process ofclaim 1 in which M is a group containing ammonium nitrogen of theformula:
 4. The process of claim 1 wherein the compound of said formulais p-chlorobenzene sulphinic acid.
 5. The process of claim 1 wherein thecompound of said formula is sodium benzene sulphinate.
 6. The process ofclaim 1 wherein the compound of said formula is zinc di-(benzenesulphinate).
 7. The process of claim 1 wherein the compound of saidformula is sodium p-chlorobenzene sulphinate.
 8. The process of claim 1wherein the compound of said formula is zinc di-(p-chlorobenzenesulphinate).
 9. The process of claim 1 wherein the compound of saidformula is zinc di-(p-toluenesulphinate).
 10. The process of claim 1wherein the selected member of said group is a synthetic rubberhomopolymer of butadiene, chlorobutadiene, dimethylbutadiene or isopreneor its homologs or a copolymer of said conjugated diolefins withstyrene, Alpha -methylstyrene, acrylonitrile, methacrylonitrile,acrylates or methacrylates.
 11. The process of claim 1 wherein theselected member of said group is a synthetic resin selected from thegroup consisting of polyethylene, polypropylene, polyvinyl chloride,polyvinyl acetate, polyvinyl chloride-acetate, polystyrene,polyacrylonitrile, acrylonitrile-butadiene-styrene copolymer,ethylene-vinyl acetate copolymer, ethylene-propylene terpolymer,ethylene-propylene copolymer, vinyl chloride-ethylene copolymer, vinylchloride-propylene copolymer and polyurethane.
 12. The process of claim1 wherein the compound of said formula is used in a mixture based onnatural or synthetic rubber in an amount of from 0.5 to 30 percent byweight based on said azodicarbonamide.
 13. The process of claim 1wherein the compound of said formula is used in a mixture based on asynthetic resin in an amount of from 0.1 to 5 parts by weight based on 1part by weight of said azodicarbonamide.
 14. A mixture comprising atleast one member of the group consisting of natural rubber, syntheticrubber and synthetic resins, a blowing agent amount of azodicarbonamideand as an activator for the blowing agent, an activating amount of acompound of the formula of claim
 1. 15. A mixture comprising at leastone member of the group consisting of natural rubber, synthetic rubberand synthetic resins, a blowing agent amount of azodicarbonamide and asan activator for the blowing agent, an activating amount of a compoundof the formula of claim 1 in which the metal cation M is an element ofthe first Main Group, the second Main or sub-Group or the fourthsub-Group of the Periodic System or a heavy metal or M is a group of theformula
 16. A mixture comprising at least one member of the groupconsisting of natural rubber, synthetic rubber and synthetic resins, ablowing agent amount of azodicarbonamide and as an activator for theblowing agent, an activating amount of Sodium benzene sulphinate.
 17. Amixture comprising at least one member of the group consisting ofnatural rubber, synthetic rubber and synthetic resins, a blowing agentamount of azodicarbonamide and as an activator for the blowing agent, anactivating amount of zinc di-(benzene sulphinate).
 18. A mixturecomprising at least one member of the group consisting of naturalrubber, synthetic rubber and synthetic resins, a blowing agent amount ofazodicarbonamide and as an activator for the blowing agent, anactivating amount of sodium p-chlorobenzene-sulphinate.
 19. A mixturecomprising at least one member of the group consisting of naturalrubber, synthetic rubber and synthetic resins, a blowing agent amount ofazodicarbonamide and as an activator for the blowing agent, anactivating amount of zinc di-(p-chlorobenzene sulphinate).
 20. A mixturecomprising at least one member of the group consisting of naturalrubber, synthetic rubber and synthetic resins, a blowing agent amount ofazodicarbonamide and as an activator for the blowing agent, anactivating amount of zinc di-(p-toluene sulphinate).